Batteries (e.g., nickel metal hydride (NiMH) batteries, lithium sulfur batteries, sodium metal hydride batteries, lithium-ion batteries, etc.) are common in, for example, home electronics, portable electronics, portable hand-tools, electric powered vehicles, etc. Lithium-ion batteries (LIBs) are one of the most popular types of rechargeable batteries for portable electronics, with a high energy density, tiny memory effect and low self-discharge. Beyond consumer electronics, LIBs are also growing in popularity for military, battery powered electric vehicles, and aerospace applications. For example, lithium-ion batteries are becoming a common replacement for lead acid batteries that have been used historically for golf carts and utility vehicles. Instead of heavy lead plates and acid electrolyte, a trend is to use lightweight lithium-ion battery packs that can provide the same voltage as lead-acid batteries, so no modification to the vehicle's drive system is required.
Lithium-ion batteries suffer severe power loss at temperatures below zero degrees Celsius, limiting their use in applications such as electric cars in cold climates and high-altitude drones. The practical consequences of such power loss are the need for larger, more expensive battery packs to perform engine cold cranking, slow charging in cold weather, restricted regenerative braking, and reduction of vehicle cruise range by as much as 40%.
For some electric-car drivers, and potential buyers, range loss of batteries (e.g., nickel metal hydride (NiMH) batteries, lithium sulfur batteries, sodium metal hydride batteries, lithium-ion batteries, etc.) in cold weather is a significant concern. “Range anxiety” is already an issue for many consumers, and potential for a loss of up to one-third of total rated range in cold weather compounds the problem.
Although the word “battery” is a common term to describe an electrochemical storage system, international industry standards differentiate between a “battery” and a “cell.” A “cell” may be a basic electrochemical unit that contains basic components, such as electrodes, a separator, and an electrolyte. A lithium-ion cell, for example, may be a single cylindrical, prismatic or pouch unit that may provide an average potential difference at associated load connection terminals of 3.7 Volts for LiCoO2 and 3.3 Volts for LiFePO4. A “battery” or “battery pack,” on the other hand, is a collection of cells or cell assemblies which are ready for use, as the battery (or battery pack) contains a housing, electrical interconnections, and possibly electronics to control and protect the cells from, for example, failure or to control heating of the battery. In this regard, the simplest “battery” may be a single cell with perhaps a small electronic circuit for protection and/or heating. In many cases, distinguishing between a “cell” and a “battery” is not important. However, this distinction is often made when dealing with specific applications, for example, in battery electric powered vehicles where “battery” may indicate a high voltage system of 400 V, and not a single cell. The term “module” is often used as an intermediate topology, with the understanding that a battery pack may be made of modules, and modules may be composed of individual cells.
In view of the above, self-heating cells and batteries are needed.